Providing material layers having a relief pattern can be done using an embossing or imprinting method such as imprinting lithography. In US 2004/0264019 A1 an exemplary method is disclosed. In the method, a relatively soft sol-gel layer is provided to a hard surfaced substrate and subjected to an embossing method for forming a pattern in the surface of the layer. To this end a stamp having a stamping surface including the complementary pattern of the desired pattern is used to emboss, i.e. to mold the desired pattern in the upper surface of the relatively soft sol-gel layer.
It is further disclosed that a suitable sol-gel solution for providing the sol-gel layer using for example spincoating in the aforementioned method may be prepared by mixing an alkoxide, e.g. a tetraalkoxysilane such as tetraethoxysilane (TEOS) or tetramethoxysilane (TMOS), water and nitric acid at molar ratios of TEOS or TMOS/water/nitric acid of 1/4-30/>0.05. The nitric acid acts as a catalyst for conversion of the TEOS or TMOS to a siliconoxide sol, which is a siliconoxide compound. After completion of the reaction butanol is added as a drying and retardation agent at molar ratios of TEOS or TMOS/water/nitric acid/butanol of 1/4-30/0.05/>4.
The spincoating process effects removal, by for example evaporation, of a portion of the solvent from the initially applied sol-gel solution. The resultant, partially dried sol-gel layer is porous and glass-like, principally comprised of silica molecular clusters together with the various solvents still present in the micropores.
It is a problem of the method described that the partially dried sol-gel layer is glass-like resulting in problematic embossing and that the resulting relief layer is porous.